Question

A comparative microarray hybridization experiment was performed between normal and cancerous cells. How will you interpret the result obtained on a microarray, if red and green coloured fluors were used for labelling the cDNA probes of normal and cancerous cells respectively?

Hint:

In microarray analysis, red indicates gene expression higher in normal cells, green indicates higher expression in cancerous cells, and yellow means equal expression.

Answer 1

In a comparative microarray experiment, cDNA from normal and cancerous cells is labeled with distinct fluorescent dyes—red for normal cells and green for cancerous cells—and then hybridized to microarray spots containing gene-specific probes. Color interpretation on the microarray:

• Red spots: Indicate genes expressed at higher levels in normal cells compared to cancerous cells (evidenced by higher red fluorescence).
• Green spots: Indicate genes expressed at higher levels in cancerous cells compared to normal cells (evidenced by higher green fluorescence).
• Yellow spots: Indicate genes expressed at equal levels in both normal and cancerous cells, resulting from the superposition of red and green signals.
• Black or absent color: Indicate genes that are not expressed or are below the detection threshold in both cell types.

Consequently, the observed color patterns on the microarray facilitate the identification of genes that are upregulated, downregulated, or unchanged in cancerous cells relative to normal cells.